The margins of the leaf-blade are somewhat hyaline and they may be perfectly even or cut into serrations of fine teeth in various ways. (See fig. 15.) In addition to these minute teeth, there may be long or short cilia. Sometimes the margins are glandular as in Eragrostis Willdenoviana and Eragrostis major.
The base of the leaf may be narrower, broader than, or about the same as the breadth of the leaf-sheath. It may be rounded, amplexicaul or narrowed. At the base and just above the ligular region there will always be a white distinct zone in the lamina of all grasses called the collar. This collar varies in length and breadth according to the species of grass.
Fig. 16.—Transverse section of leaf-buds.
A. Conduplicate; 1, 2 and 3. leaf-sheaths; 4 and 5. leaf-blades. B. Convolute; 1 and 2, leaf-sheaths; 3 and 4. leaf-blades.
In young shoots all the leaf-blades are usually found folded at the terminal portions. In most cases the leaf-blade is rolled up inwards from one end to the other so that one margin is inside and the other outside. This folding is termed convolute. This is the kind of folding that is found in most grasses. However, there are some grasses such as Eleusine ægyptiaca and Chloris barbata, in which the folding is different. In these grasses the laminas are folded flat on their midribs so that each half of the blade is folded flat on the other, the inner surfaces being in contact. The leaves are said to be conduplicate in this case. When the leaves are conduplicate the shoots are more or less compressed. (See fig. 16.)
CHAPTER III.
THE INFLORESCENCE AND FLOWER.
The flowers of grasses are reduced to their essential organs, the stamens and the pistil. The flowers are aggregated together on distinct shoots constituting the inflorescence of grasses. Sooner or later all the branches of a grass-plant terminate in inflorescences which usually stand far above the foliage leaves. As in other flowering plants, in grasses also different forms of inflorescence are met with. But in grasses the unit of the inflorescence is the spikelet and not the flower.
The forms of inflorescence usually met with are the spike, raceme and panicle. When the spikelets are sessile or borne directly along an elongated axis as in Enteropogon melicoides the inflorescence is a spike. If the spikelets borne by the axis are all stalked, however short the pedicels may be, it is a raceme. It must, however, be remembered that true spikes are very rare. An inflorescence may appear to be a spike, but on a close examination it will be seen to consist of spikelets more or less pedicelled. Such an inflorescence, strictly speaking, is a spiciform raceme. The branches of the inflorescence in Paspalum scrobiculatum or Panicum javanicum are racemes and the whole inflorescence is a compound raceme. The inflorescence is a panicle when the spikelets are borne on secondary, tertiary or further subdivided branches. Panicles differ very much in appearance according to the relative length and stoutness of the branches. In Eragrostis tremula the panicle is very diffuse, in Eragrostis Willdenoviana less so. The panicle in Sporobolus coromandelianus is pyramidal and the branches are all verticillate, the lower being longer than the upper. The branches of a panicle are usually loose, spreading or drooping in most grasses. But in some species of grasses such as Pennisetum Alopecuros and Setaria glauca, the paniculate inflorescences become so contracted that the pedicels and the short branches are hidden and the inflorescence appears to be a spike. Such inflorescences as these are called spiciform panicles. The inflorescences in several species of Andropogon consist of racemes so much modified as to appear exactly like a spike. What looks like a spike in these cases consists of a jointed axis and each joint bears a pair of spikelets, one sessile and the other pedicelled.